Burner unit in the exhaust tract of an internal combustion engine

Abstract

The invention relates to a burner unit (10) in the exhaust tract of an internal combustion engine (76) with at least one multi-path catalyst (84, 86) and / or an SCR (Selective Catalytic Reduction) system for treating the exhaust gases, wherein the burner unit (10) has at least one swirl generation device (16) integrated into an air supply (14) and a main combustion chamber (22). A pre-combustion chamber (54) is located upstream of the main combustion chamber (22), to which an ignition combustion chamber (24) with a rod-shaped ignition element (28) is assigned. The invention further relates to the use of the burner unit (10) under RDE conditions for temperature control of multi-path exhaust catalysts (84, 86) and / or particulate filters (88) in the exhaust tract of internal combustion engines (76).

Description

Technical area

[0001] The invention relates to a burner unit in the exhaust system of an internal combustion engine, comprising at least one multi-way catalyst and / or an SCR (Selective Catalytic Reduction) system for treating the exhaust gases. The burner unit comprises at least one swirl generator integrated into an air supply and a main combustion chamber. Furthermore, the invention relates to the use of the burner unit under RDE conditions for controlling the temperature of multi-way catalysts and / or particulate filters in the exhaust system of internal combustion engines. State of the art

[0002] DE 41 32 814 A1 relates to a method and a device for detoxifying exhaust gases from an internal combustion engine. In the first few minutes after starting a cold internal combustion engine, approximately 70% to 80% of the total emissions of HC and CO are emitted, since the catalyst is not yet at operating temperature. It is therefore proposed that the catalyst be heated to operating temperature by a burner system that responds to control signals from a control unit. This reduces the emissions of HC, CO, and NO. x significantly reduced.

[0003] DE 195 04 208 A1 refers to an exhaust gas converter with a catalytic converter and a burner upstream of it. The catalytic converter performs catalytic conversion of undesirable exhaust gas components only after heating to its operating temperature. For this purpose, a burner with a burner tube leading into the exhaust line and supplied with fuel and air is installed upstream of the converter to accelerate the heating of the catalytic converter and to generate further conversion of undesirable exhaust gas components in the exhaust line upstream of the catalytic converter. Areas of the burner that extend into the exhaust line are coated with catalytically active material on their surfaces exposed to the exhaust gas flow.

[0004] DE 10 2009 053 379 A1 relates to a burner. This burner is intended, in particular, for an exhaust system, especially for an internal combustion engine. The burner comprises a combustion chamber in which a mixture of an oxygen-containing gas and fuel can be combusted. A high-pressure injection valve is provided, which injects the fuel directly into the combustion chamber. Furthermore, a method for operating such a burner is proposed.

[0005] The introduction of the so-called RDE (Real Driving Emissions) boundary conditions has resulted in ambitious boundary conditions for catalytic converter heating. The now possible spontaneous cold start at high loads without an idling phase pushes previously designed in-engine catalyst heating systems to their limits, especially when further reduced emission levels, such as those expected with EU7 or an ACC 2 (Low Emission Vehicle) or LEV IV (in the USA), must be met at the same time. In this context, an exhaust gas burner for accelerating the TWC (Three-Way Catalyst, light off = start of conversion) and / or SCR (Selective Catalytic Reduction) systems has proven to be an extremely effective measure.Modern and future exhaust systems feature multiple components for purifying the exhaust gases of internal combustion engines, such as at least one, preferably two, multi-way catalytic converters and, in the case of compression-ignition internal combustion engines, SCR catalysts for exhaust gas aftertreatment, multiple lambda sensors, and particulate filters. These components all require installation space, which is very limited in modern motor vehicles. The space required to integrate these components is particularly challenging in small cars. Accordingly, the packaging requirements for additional catalyst heating systems, such as those expected to preheat the catalysts to meet the aforementioned EU7 or ACC 2 (Low Emission Vehicle) or LEV IV (in the USA), are ambitious. Description of the invention

[0006] According to the invention, a burner unit in the exhaust tract of an internal combustion engine is proposed, comprising at least one multi-way catalyst and / or an SCR (Selective Catalytic Reduction) system for treating the exhaust gases. The burner unit has at least one swirl-generating device integrated into an air supply and a main combustion chamber. A pre-combustion chamber is located upstream of the main combustion chamber, which is associated with an ignition combustion chamber with a rod-shaped ignition element.

[0007] The burner unit proposed according to the invention can in particular provide a solution having a compact construction volume, in which a distance between the pre-combustion chamber, which represents the ignition location, and an air supply is advantageously minimized.

[0008] In an advantageous development of the burner unit proposed according to the invention, the ignition combustion chamber is radially associated with the pre-combustion chamber and is in flow communication with it. The formation of the flow connection between the ignition combustion chamber on the one hand and the pre-combustion chamber on the other enables the transport of finely atomized fuel to the ignition combustion chamber, so that a stable flame extends from the pre-combustion chamber into the main combustion chamber in accordance with the flame propagation.

[0009] Advantageously, the burner unit proposed according to the invention is designed such that the swirl generating device is designed as a swirl grid and induces a spiral flow in the main combustion chamber.

[0010] In the burner unit proposed according to the invention, the pre-combustion chamber and the main combustion chamber are fluidically connected. This advantageously allows for thorough mixing of the fuel or fuel mixture atomized in the pre-combustion chamber with the air flow introduced into the main combustion chamber, generating swirl.

[0011] Advantageously, the burner unit proposed according to the invention is designed such that the spiral flow induced in the main combustion chamber is transferred into the pre-combustion chamber and imparts a spiral flow within the pre-combustion chamber to the conveying jets of a fuel or fuel mixture generated there. Thus, the solution proposed according to the invention, comprising an adjacent pre-combustion chamber and main combustion chamber, achieves a transfer of the spiral flow generated in the main combustion chamber by means of swirl into the pre-combustion chamber. As a result, the fan jets of fuel or fuel mixture generated in the pre-combustion chamber are also set in rotation, creating a spiral flow that transports the finely atomized fuel droplets into the ignition combustion chamber, where the ignition location is located.

[0012] In the burner unit proposed according to the invention, the distance between an air inlet into the main combustion chamber and an ignition point in the ignition chamber is minimized. This facilitates the extremely compact design of the burner unit proposed according to the invention.

[0013] Advantageously, in the burner unit proposed according to the invention, the air inlet is designed such that it is designed as a substantially horizontally directed air flow into the main combustion chamber or as a substantially radially directed air flow into the pre-combustion chamber or into the main combustion chamber.

[0014] In the burner unit proposed by the invention, a constricting edge is provided at the air inlet in a plane bordering the main chamber. This constricting edge can be used to achieve a corresponding constriction or wider spread of the air-fuel mixture entering the main combustion chamber.

[0015] In the burner unit proposed according to the invention, the air supply is advantageously designed in such a way that it surrounds the main combustion chamber in a jacket-like manner.

[0016] Advantageously, in the burner unit proposed according to the invention, the swirl generating device is designed as at least one swirl grid which has a swirl number in the range between 0.4 and 18, preferably between 0.6 and 15 and particularly preferably 0.9.

[0017] In the burner unit proposed according to the invention, the volume ratios of ignition chamber to pre-combustion chamber to main combustion chamber are designed such that they are in the range of 1:1:5 and 1:10:100, preferably in the range of 1:3:10 and 1:6:50 and particularly preferably 12:43:300 (1:3.6:25).

[0018] In a further advantageous embodiment of the burner unit proposed according to the invention, the design of the swirl generation device in the form of at least one swirl grid enables a separation of H2O and fuel droplets formed by condensation in the pre-combustion chamber and the main combustion chamber. In this context, the solution proposed according to the invention advantageously ensures that the main air flow does not flow past the rod-shaped heating element, but takes the direct route into the main combustion chamber. In the event that condensate has possibly formed in the burner head, which is then conveyed in liquid form by the air flow into the main combustion chamber upon restart, there is consequently only very limited opportunity for it to reach the hot surface of the rod-shaped heating element in the form of a glow plug made of ceramic material.This, in turn, significantly reduces the risk of thermal shock occurring on the surface of the ceramic material of the rod-shaped heating element. In physical terms, this phenomenon can be described by the fact that large water droplets or ligaments have poor flow-following properties and are therefore limited in their ability to follow the induced flow into the pre-combustion chamber and ultimately the ignition combustion chamber.

[0019] In a further advantageous embodiment of the burner unit proposed according to the invention, it comprises a burner housing into which an integrated cooling system, an inlet and a return line for a cooling medium are integrated. An injection device for fuel or a fuel mixture and the rod-shaped heating element can be cooled during active burner operation and heated during passive burner operation. In the embodiment described above, the cooling of all relevant components can be achieved by an inlet and a return line, thus achieving the smallest possible installation space requirement.

[0020] Furthermore, the invention relates to the use of the burner unit under RDE conditions for tempering at least one multi-way exhaust gas catalyst and / or a particulate filter which are accommodated in the exhaust tract of an internal combustion engine. Advantages of the invention

[0021] The solution proposed by the invention makes it possible to meet increasingly stringent emissions standards, which in the past could only be met through internal engine measures. However, the introduction of the so-called RDE (Real Driving Emissions) legislation results in significantly more ambitious boundary conditions for the temperature control of catalysts, such as those used in the exhaust system of internal combustion engines. The now possible spontaneous cold urban departures with high loads without an idling phase push traditional internal engine heating measures to their limits, especially if further reduced emission limits, such as those expected under EU7 or ACC 2 (Low Emission Vehicle) or LEV IV (USA) legislation, must be met at the same time.The burner unit proposed according to the invention achieves in a special way that the distance between the injection point of the fuel or fuel mixture and the ignition point can be kept as small as possible. The burner unit proposed according to the invention also makes it possible to achieve a structural functional separation with regard to the media flow in the form of the air supply, the injection of fuel or fuel mixture and the ignition point as well as the combustion chamber. Furthermore, the ignition or injection system can be advantageously protected from excessively high temperatures. In the burner unit proposed according to the invention, the ignition system is not arranged directly in the main combustion chamber, where the highest temperature is present. The flame prevailing there cannot spread from the main combustion chamber into the pre-chamber area because the incoming air prevents this.The burner unit proposed according to the invention can furthermore protect the ignition system against condensate and droplet impact when water forms and during fuel injection.

[0022] A further advantage of the solution proposed by the invention lies in increased start-up robustness, as dependencies on the swirl number of the swirl grille, the air flow rate in mass flow per hour, and the air and fuel temperatures can be reduced. Furthermore, smaller installation space requirements in the radial direction can be advantageously achieved. It is also possible to supply all media at a single location, particularly in the area of ​​the burner head.

[0023] The solution proposed according to the invention advantageously provides a burner unit that allows for modular design options, because the ignition location does not have to be individually adapted for each variant of the main combustion chamber configuration. In this way, different performance classes can be realized using the same operating principle by varying the diameter and length of the cylindrical main combustion chamber.

[0024] The burner unit proposed according to the invention results in a simplified, cost-effective production process because no add-on parts need to be mounted on the main combustion chamber in relation to the temperature of this highly stressed component, the different expansion of which would have to be taken into account in the thermomechanical design due to different thermal masses and materials.

[0025] Due to the possibility of a simple cooling or temperature control using a cooling medium, the formation of condensate in the burner head can be reduced in a particularly simple manner; conversely, defrosting can be achieved in the case of the formation of H2O in an equally simple manner.

[0026] Another significant advantage is that the main combustion chamber is surrounded by a jacket-like air supply, allowing for further tempering or preheating of the air flowing radially or horizontally into the main combustion chamber. Due to the absence of ignition (impairment point) on the combustion chamber wall, the jacket flow of the air supply is not significantly altered, ensuring an ideal, even distribution of the incoming air upon entry into the at least one swirl-generating device in the form of at least one swirl grille.

[0027] The induced swirl flow in the air supply to the main combustion chamber, caused by at least one swirl generation device, advantageously designed as a swirl grid, also induces a flow in the pre-combustion chamber, i.e. a spiral flow in the same direction of rotation. This flow formed in the pre-combustion chamber ensures that tiny atomized fuel droplets are deflected outwards from the spray mist in such a way that they then land in the ignition combustion chamber radially associated with the pre-combustion chamber and either ignite in a pre-evaporated state on a glow plug or finally evaporate on its surface and are subsequently ignited. The resulting flame front then runs to the local ignition of the mixture in the ignition combustion chamber and the pre-combustion chamber and subsequently spreads into the main combustion chamber. Short description of the drawings

[0028] Embodiments of the invention are explained in more detail with reference to the drawings and the following description. They show: Fig. 1 a representation of a burner unit according to the prior art, Fig. 2 a schematic arrangement of a burner concept proposed according to the invention with ignition combustion chamber, pre-combustion chamber and combustion chamber, Fig. 2.1 a section through the embodiment according to the invention according to Fig. 2, Fig. 3 a schematic representation of the burner unit proposed according to the invention, integrated into an exhaust tract during passive operation of the burner unit, Fig. 4 shows a variant of the burner unit proposed according to the invention with air supply at the head of the burner unit, Fig. 5 a variant of the burner unit proposed according to the invention with a radial inflow at the air inlet, Fig. 6 shows a variant of the burner unit proposed according to the invention with an air inlet into the main combustion chamber with a constricting edge, Fig. 7 shows a variant of the burner unit proposed according to the invention with a cooling circuit integrated into the burner housing, Fig. 8 shows a variant of the burner unit according to the invention with a conical insert between the pre-combustion chamber and the main combustion chamber, Fig. 9 an enlarged view of an area of ​​the Fig. 8 with the conical insert integrated between the pre-combustion chamber and the main combustion chamber, Fig. 10 shows a variant of the burner unit proposed according to the invention, in which the fuel injection device is accommodated at an angle of attack with respect to the longitudinal axis, Fig. 11.1 - 11.3 different geometric configurations of the pre-combustion chamber with a bulbous shape, a trochoid shape and a substantially conical shape and Fig. 12.1 - 12.3 Design variants of the geometry of the ignition combustion chamber in several variants.

[0029] Fig. 1 shows a burner unit 10 according to the prior art. The burner unit 10 comprises an injection device 12, a fuel or a fuel mixture. The burner unit 10 further comprises an air supply 14, via which air flows into a main combustion chamber 22 via a swirl generating device, preferably in the form of at least one swirl grid 16. The main combustion chamber 22 is assigned an ignition combustion chamber 24, which comprises a glow plug receptacle 26 for a rod-shaped heating element in the form of a glow plug 28. The main combustion chamber 22 of the burner unit 10 opens into an outlet 30. In the longitudinal axis 32 of the burner unit 10 according to the illustration in Fig. 1, the injection device 12 is oriented. Reference numeral 34 denotes an air inlet into the main combustion chamber 22. A fuel outlet 36 of the injection device 12 also opens at the air inlet 34, through which fuel or a fuel mixture enters the main combustion chamber 22. This is delimited by an end face 52 of a burner housing 56. Along the drawn longitudinal axis 32 of the burner unit 10 according to Fig. 1 shows an ignition location 38 in the ignition combustion chamber 24 as well as the air inlet 34 and the fuel outlet 36. From the illustration according to Fig. 1 shows that the ignition location 38 is located at a distance 40 with respect to the air inlet 34 and the fuel outlet 36. The fuel transport according to the illustration in Fig. 1 between the injection point, i.e., the fuel outlet 36 in the main combustion chamber 22, and the ignition point 38, here the rod-shaped heating element in the form of the glow plug 28, is significantly influenced by the interaction between the swirl flow of the air supply 14 and the injection spray(s) 20, here in the form of fan jets. For this reason, the fuel transport depends heavily on the structurally designed swirl number of the swirl grille 16, the air flow rate in the mass flow, the air or fuel temperatures, backpressure conditions in the main combustion chamber 22, as well as variations in component manufacturing and their consequences with regard to spray targeting. Embodiments of the invention

[0030] In the following description of the embodiments of the invention, identical or similar elements are designated by the same reference numerals, whereby a repeated description of these elements is omitted in individual cases. The figures only schematically illustrate the subject matter of the invention.

[0031] According to the illustration Fig. 2 shows a variant of the burner unit 10 proposed according to the invention.

[0032] In the representation of the burner unit 10 proposed according to the invention in the embodiment according to Fig. 2, the distance 40 between the ignition point 38 and the fuel outlet 36 is significantly reduced. This not only significantly reduces the size of the burner unit 10 proposed according to the invention. On the other hand, a structural functional separation is achieved with regard to the media flow, air supply 14, fuel outlet 36 and ignition point 38 with respect to the main combustion chamber 22. In the embodiment according to Fig. 2, the air supply 14 is guided in a jacket-like manner around the main combustion chamber 22. The ignition location 38 is arranged in front of the supply of the air supply 14 from the perspective of the flow direction of the air supply 14. The distance 40 between the ignition location 38 and the fuel outlet 36 into a pre-combustion chamber 54 provided according to the invention is in the embodiment according to Fig. 2 minimized. In the version according to Fig. 2, a pre-combustion chamber 54 is arranged next to the ignition combustion chamber 24. The ignition combustion chamber 24 and the pre-combustion chamber 54 are in flow communication with each other. In particular, the ignition combustion chamber 24 is arranged radially with respect to the pre-combustion chamber 54. This lies in the longitudinal axis of a burner housing 56 of the burner unit 10 proposed according to the invention, as shown in Fig. 2. The pre-combustion chamber 54 describes the volume between the injection device 12 at the fuel outlet 36 at the edge where the air supply 14 opens into the main combustion chamber 22.

[0033] Due to the swirl generating device in the form of at least one swirl grid 16, a spiral flow 50 is impressed on the air flow, which is formed in the main combustion chamber 22. Due to the flow connection between the main combustion chamber 22 and the pre-combustion chamber 54, a spiral flow 50 is also induced in the pre-combustion chamber 54, as shown in Fig. 2. This spiral flow 50 in the pre-combustion chamber 54 ensures that the smallest fuel droplets are deflected radially outward from the spray mist, so that they reach the ignition combustion chamber 24 and either ignite in a pre-evaporated state on the rod-shaped heating element 28, which may be configured as a ceramic glow plug, or finally evaporate on its surface and are subsequently ignited. A flame front emanating from the ignition location 38 leads to the local ignition of the fuel-air mixture in the ignition combustion chamber 24 and the pre-combustion chamber 54 and subsequently spreads into the main combustion chamber 22 as shown in Fig. 2 out.

[0034] Fig. 2.1 shows a section through the burner unit 10 proposed according to the invention according to the embodiment in Fig. 2. Laterally in relation to the main combustion chamber 22, the air supply 14 opens concentrically to the longitudinal axis 32 of the burner unit 10. According to the illustration in Fig. 2 runs the pre-combustion chamber 54, above which, with a slight radial offset, is the ignition combustion chamber 24 including the rod-shaped heating element 28 designed as a glow plug.

[0035] Fig. 3 is an example of a passive application of the burner unit 10 according to the illustrations in the Fig. 2 and Fig. 2.1. In the case of passive application of the burner unit 10, the cooling of the remaining exhaust gas after the burner stop, i.e. after switching off a shut-off valve 74 and transferring it to a position 80 ("closed") and possibly through continuous exchange of exhaust gas from an internal combustion engine 76 with this volume, results in water condensing out of the exhaust gas when the temperature falls below the dew point. This has the consequence that when the burner unit 10 is restarted, this water is present in the burner unit 10 either in liquid form or, depending on the temperature (< 0 °C), as ice. The liquid phase has the property that when an air pump 72 starts up, water is swirled up, thus creating the risk of thermal shock on the rod-shaped heating element 28. According to the illustration Fig. 3 further shows that the burner unit 10 is controlled by a control unit 60, which in turn is connected via a communication bus 64 to a control device 62 (ECU) of the internal combustion engine 76. Incoming air in the form of an air flow 66 passes through a filter 68, a downstream air mass meter 70, in which pressure and temperature can also be measured, before it reaches the air pump 72. In passive operation, the shut-off valve 74 is closed, ie, it assumes its position 80. According to the illustration Fig. 3 further shows that a lambda probe 78 is assigned to the internal combustion engine 76 at an inlet section 82 for exhaust gas into the main combustion chamber 22, and that a first multi-way catalyst 84 and, if appropriate, a second multi-way catalyst 86 can be located downstream of the outlet side of the internal combustion engine 76, which can be followed by a particulate filter 88. A lambda probe 42 assigned to the inlet section 82 determines the air / fuel ratio of the exhaust gas stream exiting the burner unit 10. A further lambda probe 78 assigned to an exhaust line 46 of an internal combustion engine 76 determines the air / fuel ratio of the exhaust gas from the internal combustion engine 76. Both exhaust gas streams are thus independently analyzed for their oxygen content before they mix with one another at an outlet point 44 of the inlet section 82 into the exhaust line 46 of the internal combustion engine 76.In an alternative design variant, SCR catalysts can also be used instead of multi-way catalysts, for example in self-igniting internal combustion engines (diesel).

[0036] In the representation according to Fig. 4 shows a further embodiment of the burner unit 10 proposed according to the invention. In comparison to the illustration according to Fig. 2 has a modified air supply 14. In this embodiment, all media, i.e. air and fuel, are supplied to the main combustion chamber 22 at the top of the burner housing 56 in the region of an exit plane 90. The main combustion chamber 22 itself is essentially designed as a cylindrical tube. Different diameters and combustion chamber lengths can be equipped with one and the same burner housing 56, thus allowing simple scaling and, depending on requirements, a modular system can be implemented. Here, too, the ignition combustion chamber 24 is arranged radially to the pre-combustion chamber 54, which in turn merges into the main combustion chamber 22 in the region of the exit plane 90. All combustion chambers 22, 24, 54 are fluidically connected to one another.Here, too, the spiral flow 50 of the air exiting the air supply 14, generated by the at least one swirl device 16, imparts a rotating flow in the fuel or fuel mixture within the pre-combustion chamber 54, so that atomized fuel droplets enter the ignition combustion chamber 24 and are ignited at the ignition location 38. Here, too, the distance 40 between the fuel outlet 36 and the ignition location 38 is minimized.

[0037] At a front side 52, the air emerging from the air supply 14 with a swirl essentially emerges as a horizontal air flow 92 ( Fig. 5) into the main combustion chamber 22. Regarding the dimensioning of the volumes of the ignition combustion chamber 24, pre-combustion chamber 54, and main combustion chamber 22, it should be noted that the volume ratios of the ignition combustion chamber 24 to the pre-combustion chamber 54 to the main combustion chamber 22 can, for example, be in the order of 12:43:300 (= 1:3.6:25). Example values ​​are a volume of 1215 mm3 for the ignition combustion chamber 24, of 4326 mm 3 for the pre-combustion chamber 54 and 300252 mm 3 for the volume available in the main combustion chamber 22. These values ​​are given merely as examples and can vary depending on the requirements and size of the burner unit 10 proposed according to the invention. The volume ratios of the ignition combustion chamber 24 to the pre-combustion chamber 54 to the main combustion chamber 22 can be in the range between 1:1:5 and 1:10:100, preferably in the range 1:3:10 and 1:6:50 and particularly preferably as stated above. With regard to the swirl generation device 16 in the form of at least one swirl grid, it is possible to design the swirl number in the range between 0.4 and 1.8, preferably between 0.6 and 1.9 and particularly preferably at approximately 0.9.

[0038] The Fig. 5 and Fig. 6 show further embodiments of the burner unit 10 proposed according to the invention.

[0039] Fig. 5 shows that the air supply 14 is guided around the burner housing 56 of the burner unit 10 and a swirl channel of at least one swirl generating device in the form of at least one swirl grid 16 imparts the swirl to the incoming air 14, which leads to the spiral flow 50 in the main combustion chamber 22. The fuel-air mixture is formed in the spiral flow 50, wherein the mixture formation is supported and promoted by the spiral flow 50 imposed on the air. In the illustration according to Fig. 5, a substantially radially directed air flow 94 is formed, which opens on both sides of the pre-combustion chamber 54 in the transition region of the main combustion chamber 22. The swirl generated in the main combustion chamber 22 transfers it into the pre-combustion chamber 54, which leads to the radial transport of fuel droplets or fuel mixture droplets to the ignition location in the ignition combustion chamber 24 and to the ignition taking place there. From the illustration according to Fig. 5 shows that the horizontally directed air flow 92 transitions into a radially directed air flow 94 into the combustion chamber 22. The swirl channel thus runs along the end face 52 of the air supply 14 in the transition area to the main combustion chamber 22. The edges on the boundary surfaces have an identical distance from the central axis and are essentially parallel.

[0040] Fig. 6 shows a modification of the embodiment of the burner unit 10 proposed according to the invention according to Fig. 5, that the swirl channel of the air supply 14 comprises a constricting edge 100 at the mouth into the pre-combustion chamber 54 in the burner housing 56. The edge on the side of the pre-combustion chamber 54 is further away from the central axis 120 than the edge to the main combustion chamber 22. As a result, the exiting air cone 18 is slightly constricted, so that in comparison to the exit cone 96 as shown in Fig. 5 in the version according to Fig. 6, an outlet cone 98 with a constriction is formed. Here, too, a substantially radially directed air flow 94 is deflected into a horizontally directed air flow 92 into the main combustion chamber 22. In the embodiments according to the Fig. 5 and Fig. 6, in the burner unit 10 proposed according to the invention, the ignition combustion chamber 24, the pre-combustion chamber 54 and the main combustion chamber 22 are in flow communication with one another. The transfer of the spiral flow 50 of the combustion air entering via the air supply 14 takes place analogously to the embodiment according to the above-described Fig. 2, Fig. 2.1 and 4.

[0041] Fig. Finally, Figure 7 shows a further embodiment of the burner unit 10 proposed according to the invention. In this embodiment, a geometrically compact arrangement of the ignition and injection system is shown. In addition, a simple implementation of a temperature control in the form of a cooling and heating system is shown. A cooling / heating system is integrated into the burner housing 56 of the burner unit 10, which can be supplied with a cooling medium via an inlet 112 and a return 114. The integrated temperature control 110 can, for example, cool the injection device 12 and the rod-shaped ignition element 28 in the form of the glow plug during active operation of the burner unit 10. During passive operation, as shown in the illustration according to Fig. 3, the corresponding components are tempered, ie heated, for example, by connection to the cooling medium circulating in the internal combustion engine 76, which ensures that condensate does not form on the head of the burner housing 56 of the burner unit 10 proposed according to the invention. Also in the embodiment according to Fig. 7, the ignition combustion chamber 24 with the rod-shaped heating element 28 projecting into it in the form of a ceramic glow plug, the pre-combustion chamber 54, and the main combustion chamber 22 are in flow communication with each other. The spiral flow 50 resulting from the swirl of the air supply 14 propagates into the pre-combustion chamber 54, so that the rotating fuel spray also reaches the ignition combustion chamber 24, where the ignition location 38 is located. Also in the embodiment according to Fig. 7, the ignition location 38 is located at a minimized distance 40 with respect to the fuel outlet 36 into the pre-combustion chamber 54. In the embodiment according to Fig. 7, the air supply 14 includes the swirl duct, which extends essentially radially along the end face 52 of the burner housing 56. The essentially radially directed air flow 94 in the swirl duct becomes a horizontal air flow 92, which enters the main combustion chamber 22 at the end face 52. The mechanisms of swirl transmission from the main combustion chamber 22 to the pre-combustion chamber 54 have already been explained above.

[0042] By using the Fig. The burner unit 10 shown in Figures 2 to 7 allows for a structural functional separation of the media flow in the form of the air supply 14, the fuel injection, and the ignition order with respect to the main combustion chamber 22. The ignition or injection system is protected against high temperatures because the ignition system in the form of the pilot combustion chamber 24 is not located in the main combustion chamber 22, where the highest temperatures prevail. The flame stabilized in the main combustion chamber 22 cannot spread into the pre-combustion chamber 54 because the inflowing air prevents this. Furthermore, in the burner unit 10 proposed according to the invention, the ignition system is protected from condensate and droplet impact (water and fuel).There is increased start-up robustness because dependencies on the swirl number of the at least one swirl generating device 16, the air flow rate (mass flow in kg / h), the air and fuel temperature as well as scattering and its consequences in the targeting of the spray mist are significantly reduced.

[0043] The solution proposed by the invention allows for smaller installation space requirements in the radial direction. Furthermore, it is possible to achieve a variant design using the modular principle, because the ignition location 38 does not need to be individually adapted for each combustion chamber variant. Furthermore, significant advantages arise in terms of manufacturing, since no add-on parts need to be mounted on the main combustion chamber 22, the component subject to the highest temperature loads, whose different expansions would otherwise have to be taken into account in the thermomechanical design due to different thermal masses and materials.

[0044] Finally, a further advantage of the burner unit 10 proposed according to the invention is an easily implemented integrated temperature control 110 as cooling or heating, so that the formation of condensate and icing in the area of ​​the burner head can be effectively counteracted.

[0045] Fig. 8 shows a further embodiment of the burner unit 10 proposed according to the invention, in which a cone or a conical piece 126 is arranged between the pre-combustion chamber 54 and the main combustion chamber 22.

[0046] The Fig. The conical piece 126 indicated in Figure 8 is located between the exit of the pre-combustion chamber 54 and the end face 52, which defines the main combustion chamber 22. A mixture is formed in the latter, supported by the spiral flow 50 of the air, which consists of the fuel injected via the fan jets 20 on the one hand and the combustion air entering via the air inlet 34 on the other hand. Otherwise, the conditions according to Fig. 8 those in the figures already described above.

[0047] Fig. 9 shows an enlarged view of the conical piece 126. A first dimension v 116 designates the opening of the conical piece 126 at the end of the pre-combustion chamber 54. A further, second dimension H 118 designates the diameter of the conical piece 126 at the end face 52, which delimits the main combustion chamber 22. The advantage of this arrangement is that, due to the assumption of v < H, the fuel cannot be injected directly into the channel of the inflowing air because this channel lies behind an imaginary line between the injection location and the edge at the distance v.

[0048] Fig. 10 shows a further embodiment of the burner unit 10 proposed according to the invention, in which the injection device 12 in the form of a fuel injector is arranged inclined at an angle of attack α 122 with respect to a central axis 120. To optimize the installation space, the injection device 12 is arranged at said angle of attack 122 with respect to the central axis 120. The injection jets 20 (cf. fan jet) are corrected in the spray targeting. Consequently, it is possible to use the rod-shaped heating element 28, as shown in Fig. 10, in a parallel arrangement 124 with respect to the central axis 120 of the burner unit 10. This means that the rod-shaped heating element 28 in the form of a glow plug made of ceramic material is placed axially parallel to the central axis 120. This results in a minimal installation space requirement. In this Fig. 10, it is also possible to dimension the diameter of the burner head smaller than the cylinder of the main combustion chamber 22. Fig. 11.1 to 11.3 show various geometries 128 of the pre-combustion chamber 54.

[0049] In relation to Fig. 11.1, the pre-combustion chamber 24 is designed in a geometry 128 that has a bulbous configuration 130. This means that the wall surfaces of the pre-combustion chamber 54 are not cylindrical, but slightly curved.

[0050] Fig. 11.2, in contrast, shows that the boundary wall of the pre-combustion chamber 54 has a different geometry 128, namely a trochoid shape 132. The trochoid shape 132 can advantageously support the acceleration of the fuel flow, ie, the fuel emerging in the form of fan jets 20, and its swirling.

[0051] Fig. 11.3 shows the design variant of the pre-combustion chamber 54 in that it is designed in a geometry 128 that deviates from the cylindrical shape in the form of a conical shape 134 with rounded sections that merge into one another.

[0052] The Fig. Finally, Figures 12.1 to 12.3 show various geometries 136 in which the ignition combustion chamber 24 is designed. This is always shown as box-shaped in the preceding figures, but can also have curved wall areas, as is shown by the first geometry 138 in Fig. 12.1, a second geometry 140 in Fig. 12.2 and in a third geometry 142 in Fig. 12.3. Rounded surfaces promote flow conditions and prevent disruptive vortex formation and flow effects.

[0053] The invention is not limited to the embodiments described here and the aspects highlighted therein. Rather, numerous modifications are possible within the scope of the claims, which are within the scope of expert practice. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 41 32 814 A1

[0002] DE 195 04 208 A1

[0003] DE 10 2009 053 379 A1

[0004]

Claims

[1] Burner unit (10) in the exhaust tract of an internal combustion engine (76) with at least one multi-way catalyst (84, 86) and / or an SCR system (Selective Catalytic Reduction) for treating the exhaust gases, wherein the burner unit (10) has at least one swirl generating device (16) which is integrated into an air supply (14) and has a main combustion chamber (22), characterized by that the main combustion chamber (22) is preceded by a pre-combustion chamber (54) to which an ignition combustion chamber (24) with a rod-shaped ignition element (28) is assigned. [2] Burner unit (10) according to claim 1, characterized by that the ignition combustion chamber (24) is radially associated with the pre-combustion chamber (54) and is in flow connection with it. [3] Burner unit (10) according to claims 1 and 2, characterized by that the swirl generating device (16) is designed as a swirl grid and induces a spiral flow (50) in the main combustion chamber (22). [4] Burner unit (10) according to claims 1 to 3, characterized by that the pre-combustion chamber (54) and the main combustion chamber (22) are fluidically connected to each other. [5] Burner unit (10) according to claims 1 to 4, characterized by that the spiral flow (50) induced in the main combustion chamber (22) is transferred into the pre-combustion chamber (54) and imposes a spiral flow (50) in the pre-combustion chamber (54) on the fan jet (20) of a fuel or a fuel mixture generated there. [6] Burner unit (10) according to claims 1 to 5, characterized by that a distance (40) between an air inlet (34) into the main combustion chamber (22) and an ignition location (38) in the ignition combustion chamber (24) is minimized. [7] Burner unit (10) according to claims 1 to 6, characterized bythat the air inlet (34) takes place as a substantially horizontally directed air flow (92) into the main combustion chamber (22) or as a substantially radially directed air flow (94) into the pre-combustion chamber (54) and / or into the main combustion chamber (22). [8] Burner unit (10) according to claims 1 to 7, characterized by that a constricting edge (100) is provided at the air inlet (34) in an outlet plane (90) delimiting the main combustion chamber (22). [9] Burner unit (10) according to claims 1 to 8, characterized by that the air supply (14) is designed in a jacket-like manner surrounding the main combustion chamber (22). [10] Burner unit (10) according to claims 1 to 9, characterized by that the swirl generating device (16) is designed as a swirl grid which has a swirl number which is in the range between 0.4 and 1.8, preferably between 0.6 and 1.5 and particularly preferably 0.

9. [11] Burner unit (10) according to claims 1 to 10, characterized by that volume ratios of ignition combustion chamber (24) to pre-combustion chamber (54) to main combustion chamber (22) are in the range between 1:1:5 and 1:10:100, preferably in the range between 1:3:10 and 1:6:30, particularly preferably 12:43:300 (1:3.6:25). [12] Burner unit (10) according to claims 1 to 11, characterized by that a separation of drop-shaped H2O occurs between the pre-combustion chamber (54) and the main combustion chamber (22). [13] Burner unit (10) according to claims 1 to 12, characterized by in that it comprises a burner housing (56) into which an integrated cooling means (110), an inlet (112) and a return (114) of a cooling medium are integrated, wherein an injection device (12) and the rod-shaped heating element (28) can be cooled in active burner operation and heated in passive operation. [14] Use of the burner unit (10) according to one of claims 1 to 13 under RDE conditions for separating multi-way exhaust gas catalysts (84, 86) and / or particle filters (88) in the exhaust tract of internal combustion engines (76).

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